From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752262AbaIAAOx (ORCPT ); Sun, 31 Aug 2014 20:14:53 -0400 Received: from lgeamrelo04.lge.com ([156.147.1.127]:49965 "EHLO lgeamrelo04.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752238AbaIAAOv (ORCPT ); Sun, 31 Aug 2014 20:14:51 -0400 X-Original-SENDERIP: 10.177.222.131 X-Original-MAILFROM: iamjoonsoo.kim@lge.com Date: Mon, 1 Sep 2014 09:15:26 +0900 From: Joonsoo Kim To: Naoya Horiguchi Cc: Andrew Morton , "Kirill A. Shutemov" , Rik van Riel , Peter Zijlstra , Mel Gorman , Johannes Weiner , Minchan Kim , Yasuaki Ishimatsu , Zhang Yanfei , "Srivatsa S. Bhat" , Tang Chen , Bartlomiej Zolnierkiewicz , Wen Congyang , Marek Szyprowski , Michal Nazarewicz , Laura Abbott , Heesub Shin , "Aneesh Kumar K.V" , Ritesh Harjani , t.stanislaws@samsung.com, Gioh Kim , Vlastimil Babka , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH v3 4/4] mm/page_alloc: restrict max order of merging on isolated pageblock Message-ID: <20140901001525.GC25599@js1304-P5Q-DELUXE> References: <1409040498-10148-1-git-send-email-iamjoonsoo.kim@lge.com> <1409040498-10148-5-git-send-email-iamjoonsoo.kim@lge.com> <20140829165244.GA27127@nhori.bos.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140829165244.GA27127@nhori.bos.redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 29, 2014 at 12:52:44PM -0400, Naoya Horiguchi wrote: > Hi Joonsoo, > > On Tue, Aug 26, 2014 at 05:08:18PM +0900, Joonsoo Kim wrote: > > Current pageblock isolation logic could isolate each pageblock > > individually. This causes freepage accounting problem if freepage with > > pageblock order on isolate pageblock is merged with other freepage on > > normal pageblock. We can prevent merging by restricting max order of > > merging to pageblock order if freepage is on isolate pageblock. > > > > Side-effect of this change is that there could be non-merged buddy > > freepage even if finishing pageblock isolation, because undoing pageblock > > isolation is just to move freepage from isolate buddy list to normal buddy > > list rather than to consider merging. But, I think it doesn't matter > > because 1) almost allocation request are for equal or below pageblock > > order, 2) caller of pageblock isolation will use this freepage so > > freepage will split in any case and 3) merge would happen soon after > > some alloc/free on this and buddy pageblock. > > > > Signed-off-by: Joonsoo Kim > > --- > > mm/page_alloc.c | 15 ++++++++++++--- > > 1 file changed, 12 insertions(+), 3 deletions(-) > > > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > index 809bfd3..8ba9fb0 100644 > > --- a/mm/page_alloc.c > > +++ b/mm/page_alloc.c > > @@ -570,6 +570,7 @@ static inline void __free_one_page(struct page *page, > > unsigned long combined_idx; > > unsigned long uninitialized_var(buddy_idx); > > struct page *buddy; > > + int max_order = MAX_ORDER; > > > > VM_BUG_ON(!zone_is_initialized(zone)); > > > > @@ -580,18 +581,26 @@ static inline void __free_one_page(struct page *page, > > VM_BUG_ON(migratetype == -1); > > if (unlikely(has_isolate_pageblock(zone))) { > > migratetype = get_pfnblock_migratetype(page, pfn); > > - if (is_migrate_isolate(migratetype)) > > + if (is_migrate_isolate(migratetype)) { > > + /* > > + * We restrict max order of merging to prevent merge > > + * between freepages on isolate pageblock and normal > > + * pageblock. Without this, pageblock isolation > > + * could cause incorrect freepage accounting. > > + */ > > + max_order = pageblock_order + 1; > > When pageblock_order >= max_order, order in the while loop below could > go beyond MAX_ORDER - 1. Or does it never happen? Yes, you are right. Will fix it in next spin. Thanks.